The present invention is related to tyrosylprotein sulfotransferases and polynucleotides which encode said tyrosylprotein sulfotransferases.
Tyrosine O-sulfation is a post-translation modification of membrane and secretory proteins that occurs in all multicellular eukaryotes (1-3). The enzyme required for this reaction, called tyrosylprotein sulfotransferase (TPST), catalyzes the transfer of sulfate from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to tyrosines within highly acidic motifs of polypeptides (2,4). Evidence has previously indicated that the enzyme is a membrane-associated protein with a lumenally oriented active site localized in the trans-Golgi network (5,6).
Many proteins have been shown to contain tyrosine sulfate. Among these are several proteins involved in inflammation and hemostasis, including PSGL-1 (7), the .alpha.-chain of complement factor C4 (8), coagulation Factors V (9) and VIII (10,11), platelet glycoprotein Ib.alpha. (12,13), .alpha..sub.2 -antiplasmin (14), and heparin cofactor II (15). Although the role of tyrosine O-sulfation is incompletely understood, it is clear that tyrosine O-sulfation plays a role in protein-protein interactions in several systems. Tyrosine O-sulfation is required for the optimal interaction between Factor VIII and Von Willebrand factor (10,11), PSGL-1 and P-selectin (7), GPIba with Von Willebrand factor and .alpha.-thrombin (12,13), and complement factor C4 and C1s (8).
The kinetics of the TPST reaction has been studied using crude and partially-purified enzyme preparations from a variety of mammalian tissues (18,19). However, it has not been clear whether TPST activity is due to one enzyme or a family of enzymes. Two groups have previously reported attempts to purify TPST (20,21). However, neither group was able to sufficiently purify the protein to identify its amino acid sequence, nor have cDNAs encoding the enzyme previously been identified. As a result, there has remained a need in the field for complete identification of TPST and of cDNAs encoding TPST.